一组可用于探测亚稳态橄榄石存在情况的震相  

A group of distinct seismic phases that could be used to detect metastable olivine

作　　者：叶国扬[1] 楼小挺[1] 王彦宾[1] 宁杰远[1] 

机构地区：[1]北京大学地球与空间科学学院地球物理学系,北京100871

出　　处：《地球物理学报》2008年第4期1165-1171,共7页Chinese Journal of Geophysics

基　　金：国家自然科学基金(40774034;90814002);地震科学联合基金(105125)资助

摘　　要：基于简化的波速结构,利用二维伪谱法研究了俯冲带不同位置震源激发的地震波的传播特征.发现当俯冲板块中存在6%的低速异常时,直达P波和直达S波之间存在波阵面近平面的易于识别的P-S转换震相.其传播方向不因震源位置偏离低速层的中心而改变.对于低速层的边界存在±2 km的随机起伏、低速层为楔形、周围介质为水平分层模型这三种情况,这组震相仍然清晰可辨.对于150 km长度的橄榄石楔,模拟结果显示仍然能在一定震中距范围内接收到这一震相.因此,可以尝试用这组震相来探测俯冲带亚稳态橄榄石的存在状态.We employ a 2-D pseudo-spectral code to study the seismic wave propagation in subduction zones, in which the deep earthquakes that generate the seismic waves are located at different places in subduction slabs. A group of easy to detect P-S converted phases with planar wave front emerges between P and S phases when a high wave speed slab has a 6% low velocity rectangular zone in it. The propagation directions of these phases are only related with the wave velocities of the materials located in two sides of the contact interface. It keeps the same when the hypocenter location deviates from the center of the slab. These phases are still very clear when the boundaries of the low velocity zone are uneven, e. g. , with ±2 km undulation, when the low velocity zone changes to wedge shaped, when the surrounding mantle has PREM structure. For a 100-200 km long low velocity wedge, these phases are still detectable. So, we suggest people to employ these phases to detect metastable olivine in subduction zones.

关 键 词：俯冲带 亚稳态橄榄石 地震波 数值模拟 伪谱法 

分 类 号：P631[天文地球—地质矿产勘探]